The traffic-flow problem in two dimensions is formulated as a three-st
ate model on a square lattice in terms of Pauli operators. Using a Poc
k-space representation of the master equation we get the Liouvillian f
or the problem with asymmetric exclusion. Three different realizations
, symmetric, right-before-left model and an exchange model will be ana
lysed within the mean-field approximation (MFA). The resulting kinetic
equations for the average occupation number of cars in the upward and
sideward directions are coupled. The average velocity can be calculat
ed in MFA. It results in a jamming transition that depends on the tota
l concentration of cars.